The National Institute of Child Health and Human Development (NICHD) is conducting a Phase III multicenter, open-label, non-comparative trial (Protocol number: CCN008; A Multicenter, Open-Label, Non-Comparative Study of the Safety and Contraceptive Efficacy of the Woman's Condom) to determine the contraceptive efficacy ofthe Woman's Condom (WC). A secondary objective of the trial is to assess the perfonnance of the WC in a subset of women by evaluating whether a biological marker of semen exposure (i.e., prostate-specific antigen (PSA)) is present in postcoital vaginal fluid specimens. Detection of the semen biomarker in the vagina following the use of a female condom may be a more sensitive measure of female condom failure as a barrier than either pregnancy or infection. The Biomarker Substudy will be nested within the CCN008 trial. NICHD will enroll a subset of subjects (N=150) to collect vaginal swabs and the used female condoms for testing for PSA detection. Each of the 150 subjects is to provide three specimens (pre and post-coital swabs and the used condom) for each of four acts. Thus, an estimated 1,800 specimens will be tested for PSA.